well, the difference is all the stuff you would pass that are owned and operated by entities other than Universal. Whereas, for the most part, everything you pass when going from one Disney Park to another Disney Park is owned and operated by Disney
So I do get what
@tlmadden73 is saying - going from Islands of Adventure and then passing a Golden Corral and Ripley's Believe it or Not or Pirate Cove Adventure Golf to get to this new Universal Park does feel like leaving a contained "resort" and going to something else
Not holding it against them or saying it is horrible or anything, but I do get that it provides a different feeling. Guess it is the same thing as those that want to stay "in the Disney Bubble" their entire vacation vs staying offsite to Disney